Change #include style

Header files are now always included with their path from the
project's root directory rather than the path relative to
the includer.

Change-Id: If39b8510eef8da00baf5fe88337c45dbdf8c766e
Refs: #3084
diff --git a/tools/ndnsec/util.cpp b/tools/ndnsec/util.cpp
index b97e934..f5069e7 100644
--- a/tools/ndnsec/util.cpp
+++ b/tools/ndnsec/util.cpp
@@ -21,7 +21,7 @@
 
 #include "util.hpp"
 
-#include <ndn-cxx/security/detail/openssl.hpp>
+#include "ndn-cxx/security/detail/openssl.hpp"
 
 namespace ndn {
 namespace ndnsec {